Geochemical analysis of formation water as a tool for better understanding of water flooding

Abstract

Abstract In oil production, a reservoir flooding system is often used. This is necessary to compensate for oil production in the reservoir and maintain reservoir pressure. But the water cutting of wells is constantly increasing, that makes the exploitation less profitable, in the future this leads to the shutdown of wells. The source of water supply to the well is not always clear, and in the presence of flooded below and overlying reservoirs from which production was previously carried out, the possible number of water supply routes increases. The first aim of this work is to identify channels with high permeability by using tracer test, the second aim is to characterize geochemical state of the reservoir as a whole, and finally to choose the optimal sidetrack point using reservoir modelling. The reservoir represents terrigenous deposits as an independent Bobrikovian horizon and the incision channel in the carbonate massif. The permeability of these zones is expected to be different. Therefore, in order to achieve the aims, the following studies were conducted: 1) Tracer test. A tracer blindly follows the fluid phase in which it is injected. Tracer tests are most often used to obtain information on the direction and velocity of the flow of brines, hydraulic conductivity, effective porosity, transport parameters (e.g., dispersivity values), and the presence of preferential flow paths. For this, we used a spectrofluorimeter. 2) Geochemical studies of the composition of all wells on the site. A unified Oil Water Contact (OWC) for carbonate and terrigenous deposits indicates the possibility of their hydrodynamic communication. To confirm this hypothesis, areal geochemical studies of the isotopic composition of reservoir waters were carried out; 3) Using the previous methods, we conducted a Field Development Analysis (FDA) and modeled the position of the horizontal wellbore in special software. One well showed better results compared to the other, as it is located in a zone with large oil reserves and the length of the horizontal wellbore was 1.3 times longer. As a result of geochemical studies, three zones were identified based on the isotopic composition of water: the southwest - the waters of the Bobrikovian horizon, the central part - the transition zone, and the northeast - the Tournaisian waters. Zones with current reserves have been determined based on 3D modeling. For further involvement of these volumes of reservoir oil in the development, the sidetracking is proposed.